1. Field of the Invention
The present invention relates to a gas laser generator, and, specifically, to a gas laser generator which gives a uniform and stable discharge in the discharge region.
2. Description of the Related Art
Conventionally, a triaxial transverse type of gas laser generator for example, is known. In this gas laser generator the gas flows in the predetermined direction (Z-axis direction) of the discharge region, while a mirror system for an optical resonator and positive and negative discharge electrodes are respectively positioned in opposition in two directions at right angles (X-axis direction, Y-axis direction), interposing the gas flow.
The mirror system is usually the so-called folded type of optical resonator for improving the gain of the optical resonator. In the optical resonator, for example, a rear folding mirror and a front folding mirror are positioned, as a pair, in opposition on both the right and left sides, interposing the gas flow. A primary mirror is positioned adjacent to the downstream side of the rear folding mirror with reference to the gas flow. In addition, an output mirror is positioned adjacent to the upstream side of the front folding mirror with reference to the gas flow.
Accordingly, the optical cavity of the optical resonator, which is interposed by the mirror system, has a uniform width parallel to the gas flow, and the laser beam is uniformly amplified within the upstream gas flow and the downstream gas flow in this cavity.
The discharge electrodes are positioned in multiple locations in a two-dimensional expanse on both the top and bottom sides of the optical cavity in order to uniformly excite the gas flowing in the optical cavity.
The ions generated at a uniform excitation discharge of the upstream electrodes in this type of discharge device stream to the vicinity of the electrode on the downstream side, so that the resistance in the electrode gap on the downstream side declines tremendously, and the discharge deviates toward the downstream side. The downstream discharge proceeds in a localized arc, giving rise to the problem that instability could be produced in the excitation discharge.
In addition, even if the arc discharge does not shift, there is also the problem that irregularities are produced in the discharge, and various inconveniences are produced in the laser output and mode pattern.
Ballast resistances (stable resistances) are connected to a plurality of electrodes which are positioned in a two-dimensional expanse to provide stability of discharge.
The power consumed by this ballast resistance during laser generation amounts to several KW and a large amount of heat is generated. Accordingly, the ballast resistances which are connected to each of the electrodes are housed in a cooling receptacle filled with insulating oil which cools them. The number of ballast resistances must be the same as the number of electrodes, and, for a unit provided with simmer resistances, the same number of resistances are added. In addition, there are also units in which the same number of diodes are provided. Accordingly, the wiring between the resistances and elements in the cooling receptacle becomes extremely complex, and, also, it is difficult to cool the individual ballast resistances uniformly so that the stability of the discharge is a problem area.